Cancer remains one of the scourges of mankind and radiation therapy is one of the chief tools to combat same. In radiation therapy a high energy treatment radiation beam is used to destroy cancerous tissue whilst sparing healthy one.
A particular type of radiation therapy planning called Intensity Modulated Radiotherapy (IMRT) allows spatially modulating a treatment beam to precisely conform not only in shape but also in terms of prescribed dosage requirements as per a treatment plan.
A treatment plan is computed using numerical optimization based on an objective function that defines a number of dose objectives or dose-volume objectives. Although a plan may globally comply with these objectives, there may still remain local deficiencies. For instance, some parts of the cancerous region may receive more than the required dose or may receive less than the required dose.
Although there are systems to “tweak” an existing treatment plan (see for instance C Cotrutz and L Xing, “IMRT dose shaping with regionally variable penalty scheme”, Med. Phys. 2003; 30 544-51), these are sometimes not easy to operate. Any modification made to the beam arrangement or the objective function parameters of the current treatment plan in view of removing such local deficiencies could lead to big changes in the dose distribution. In particular, the magnitude and type of change is beyond the direct influence of the user and could lead to several manual backtracking steps.